In the operating environment of a turbine section of a turbomachine such as a gas turbine, the structural integrity of various turbine components such as turbine rotor wheels, rotor blades, rotor shaft and other components within the turbine section is of great importance to turbomachine operators. As the turbomachine cycles between various operating conditions such as start-up, shut-down, base-load or part-load operation, the various turbine components are subjected to high thermal and mechanical stresses. As a result, it is necessary to inspect, repair and/or replace the various turbine components during regularly scheduled maintenance intervals or during unplanned outages to prevent component failures. However, access to the various turbine components may be challenging, particularly for a turbomachine that is installed at an owner/operator's facility.
The construction of turbine sections that utilize multiple casings has become a common approach for facilitating the on-site maintenance of land-based gas turbine engines. As known in the art, turbines having this type of construction include an inner casing surrounded by an outer casing, and frames that are split on the machine horizontal centerline, such that upper halves of the inner and outer casings, and frames may be lifted individually for access to internal parts of the turbine. For example, by lifting the upper halves of the turbine inner and outer casings, the turbine rotor wheels, buckets and nozzle assemblies can be inspected and possibly repaired or replaced without necessitating removal of the entire turbine rotor. Prior to casing removal, proper machine centerline support using mechanical jacks is necessary to assure proper alignment of the rotor and to obtain accurate casing clearances. In particular instances, the mechanical jacks provide support to the lower half casing.
The removal and reinstallation of the lower half of the turbine inner casing for the purpose of conducting a complete inspection of the turbine section present significant challenges to maintenance personnel. For example, work space may be significantly limited in the location of the lower half of the turbine casing. In addition, very tight tolerances exist between the turbine rotor blades and the lower half of the inner casing, thereby increasing the risk of damage to the various turbine components positioned within the lower half of the casing. Therefore, an improved system for installing and uninstalling the lower portion of the inner turbine casing of a gas turbine engine would be useful.